It seems that the authors have up-dated the works of Nikolai Kondratieff.
A segment from a much earlier study appears below, the link to the full document is below . It includes an excellent graphic on the waves over time without a lot of reading
Thanks for the up-dated projections.
“Since the 18th century, economists have identified five Kondratieff Waves, with the first wave occurring during the invention of the steam engine and lasting from 1780 to 1830.”